High molecular weight hydrocarbon soluble polymers such as polyisobutylene, polystyrene, and several poly .alpha.-olefins have been demonstrated to reduce drag in turbulent flows of hydrocarbon liquids. Generally, the drag reduction effectiveness of these polymers improves with increasing molecular weight; however, the tendency for the polymers to permanently degrade via molecular scission in local extensional flows within pumps or turbulent pipeflows also increases with increasing polymer molecular weight. This invention discloses efficient drag reduction in hydrocarbon liquids resulting from a novel class of interpolymer complexes which are prepared by a unique and novel process containing, for example, a styrene/vinyl pyridine (SVP) random copolymer and a randomly sulfonated ethylene propylene diene monomer (S-EPDM) copolymer. These complexes can provide improved drag reduction via enhanced molecular interactions rather than increased molecular weight and, consequently, may be less sensitive to flow degradation.
Drag reduction in turbulent flow can be achieved by the addition of minor amounts of a very high molecular weight polymer which is soluble in the fluid of interest. Copending application, entitled "Drag Reduction Agent for Hydrocarbon Liquid", Ser. No. 547,909, filed the same day as this application, describes drag reduction obtained by addition of a novel interpolymer complex derived from a combination of cationic and anionic polymers. In such interpolymer complexes, the polymers used may be of lower molecular weight, but the size of the complex rather than molecular weight controls drag reduction efficiency.
Normally, drag reduction is demonstrated by dissolving the high molecular weight polymer in the fluid prior to subjecting it to flow in which drag is reduced. In this invention, it is disclosed that when an interpolymer complex or other multi-ingredient additives are used for drag reduction, the preparation sequence of the solution, or the introduction method and sequence, can significantly affect drag reduction efficiency and that given schemes will be advantageous.